#include <iostream>
using namespace std;
int main ()
{
    int N;
    cout<<"Vvedite chislo"<<endl;
    cin>>N;
    int j;
    if (N%2==0)
        j=2;
    else
        j=1;
    int F=1;
    while (j<=N)
    {
        F=F*j;
        j=j+2;
    }
    cout<<F;
}
